The House of Hope stands on land cleared by a tornado that roared through the woods a few years ago near this little town. But the vulnerable children inside are more concerned with man-made dangers. In this corner of rural America something out there is much worse than a twister: it is called crystal meth.

Known as crank or ice, meth is the latest drug epidemic to hit America. Following hard on such scourges as heroin and crack, meth has taken a stranglehold on large swathes of the US. Unlike its predecessors, it is not found in inner-city ghettos but in the mostly white rural heartland of states such as Iowa, Missouri and Tennessee, devastating such places as Cumberland County, a picturesque place of rolling forests overshadowed by the Smoky Mountains.

The House of Hope, near Crossville, looks after some of the innocent victims. Dubbed 'meth orphans', they are children taken into care when their parents are arrested and jailed. They have usually grown up in 'meth labs', home factories for making the drug, and have suffered terrible mental and physical abuse. The House provides temporary refuge until foster parents can be found.

The need is great. In the last six months more than 60 meth orphans have come through the doors. All are from Cumberland County, whose population is just 50,000. 'We are at the epidemic stage in Tennessee. It is terrible,' said Mike Steinmann, head of the orphanage, standing in a room full of toys donated by local people.

Across rural America, meth is reaping a terrible toll. In the past five years Tennessee, West Virginia, Kentucky and North Carolina have seen the number of meth labs grow tenfold, and 58 per cent of US sheriffs' departments now say meth is their biggest drug problem, compared to 19 per cent who name cocaine and 3 per cent who say heroin. More than 80 per cent of prison inmates in one county of Indiana are there for meth-related crime.

The drug has changed the nature of some states' jail populations. Arkansas, which used to have a black majority, now finds most inmates are white. There are also signs that meth is spreading from rural areas, entering the suburbs and continuing its onslaught as America's number one drug crisis.

Cumberland is a typical county at the centre of the storm. Its burly sheriff, Eucle 'Butch' Burgess, reeled off huge increases in crime since meth appeared in 1999. Violent offences have jumped by 500 per cent, petty crime by 600 per cent and domestic violence by 500 per cent. The county jail is full to bursting and a new wing is being planned. Female prisoners, once a rarity, are now common. 'One man was so addicted he begged me not to let him out of jail because he knew he would go straight back to it,' Burgess said.

This has stretched the county's finances to breaking point, and the sheriff believes the effects of the epidemic will last for a generation or more: 'If you could push a button and stop producing meth right now, we would still be dealing with the aftermath for the next 20 years or more.'

Meth is powerfully addictive, instantly hooking users who smoke or inject it and turning them into paranoid delusional wrecks with scabs from constant scratching and dramatic weight loss. One of the worst symptoms is 'meth mouth' which causes users to lose all their teeth, sometimes in a few months.

Yet it gives a huge high and enough energy to stay awake for several days. More important, it is made from ingredients found in cough medicines and matches, allowing it to be made in 'mom and pop' home operations with supplies bought from supermarkets. Dubbed the 'poor man's cocaine', it is cheap, at just $50 (£27.50) a gram.

For Burgess, the real victims are the meth orphans who come through the doors of the House of Hope. Their parents, obsessed with making and taking the drug, ignore their children, often forgetting to feed or clothe them. In one case children in a home meth lab were so hungry they ate the plaster from the walls. Even more horrifying, the drug gives sex drives a powerful boost, making sexual abuse common in meth addicts' homes.

Faced with such horrors, Sheriff Burgess and his wife have fostered more than 30 of Cumberland's meth orphans in their own home. 'It is the hardest but best thing I have ever done,' he said.

The couple are now trying to adopt one boy . The sheriff showed photographs of the boy. In the first he looks terrified, pale and thin with a sore on his face. Later pictures show him at his fifth birthday party, filling out, with a broad smile on his face.

'I just wanted something positive out of this terrible situation, and there he is,' Burgess said.

The hard facts

Crystal meth is a colourless, odourless form of d-methamphetamine, a powerful and highly addictive stimulant. It's typically smoked using a glass pipe, but may be injected. It's also known as Tina, hot ice, LA glass or LA ice, shards and shabu.

It typically resembles small fragments of glass or shiny white-blue 'rocks' of varying sizes, but is also available in powderform.

Smoking or injecting it produces an immediate high which may last 12 hours or more.

Nearly 5 per cent of US high school seniors say they have used it at least once

Although it can be produced easily with household chemicals, it is illegal both in the US and the UK. In Canada, the penalty for making it was raised last week to life imprisonment.